The Mechanism of Free-Sector Rent Increases
A 'CPI-adjusted lease' is a rental agreement that contains an indexation clause specifically linking the annual rent increase to the Consumer Price Index (CPI). The CPI, or Consumentenprijsindex in Dutch, is the official measure of the average change in prices paid by households for a basket of consumer goods and services. It is the official measure of inflation. This is the most common and accepted mechanism for adjusting rent in the free rental sector (vrije sector). By tying the rent increase to this official statistic from the Centraal Bureau voor de Statistiek (CBS), the process is made objective and transparent, preventing arbitrary rent hikes by the landlord.
How to Calculate the Increase
The rental contract will specify the formula. A typical clause might read: "The rent will be adjusted annually, for the first time on July 1, 2026, by a percentage equal to the percentage change of the CPI (all households) for the calendar year preceding the adjustment, plus a maximum of 1%."` To calculate the new rent, you would find the official CPI percentage published by the CBS for the relevant period, add any contractually agreed-upon markup (up to the legal cap), and apply that total percentage to your current basic rent. The landlord must provide you with this calculation in their written notice of the rent increase.
The Legal Cap is King
As of August 2025, all tenants should be aware of the legal cap on free-sector rent increases. Even if your contract from a few years ago specifies a higher markup (e.g., CPI + 4%), the current law limits the increase to CPI + 1%. The law overrides the contract. This cap provides significant protection, especially in times of high inflation. Tenants should always check the legally permitted maximum for the current year before agreeing to a rent increase proposed by their landlord.